18. Kather, R. & S.J. Martin – FRIEND OR FOE? NESTMATE RECOGNITION IN THE HONEY BEE APIS MELLIFERA - Honey bees can tell nestmates from non-nestmates and chase away any intruder trying to enter their hive. Despite this, one of the honey bee’s major and most lethal parasites, the Varroa mite, frequently enters and travels between hives. To determine how Varroa is able to overcome the bees’ detection system we need to better understand how bees recognize each other. Insects use their sense of smell to identify other insects. Every insect produces a set of chemicals on their ‘skin’, so-called cuticular chemicals, and usually insect species differ in the type of chemicals they produce (Howard & Blomquist, 1982 Ann. Rev. Entomol. 27:149-172). In the social insects such as wasps, hornets and bees, colonies of the same species produce the same types of chemicals, but chemical quantities vary between colonies forming a colony-specific odor. This way, one insect can identify another insect, i.e. which species or colony it belongs to, by ‘reading’ the chemicals on that insect’s skin. Chemically, Varroa ‘looks’ like a honey bee, which partly explains why it remains undetected in the hive, but how does it overcome the bees’ colony recognition when it moves between hives? To answer this question we need to identify the compounds bees use to identify nestmates.

Previous studies have suggested two candidate classes: the fatty acids and the alkenes (Breed & Stiller, 1992 Anim. Behav. 43:875-883, Dani et al., 2005 Chem. Senses 30:477-489). But chemical evidence to support this is still missing. Our research was the first to see whether nestmates had similar quantities of fatty acids/alkenes and whether colonies varied in these quantities, which we would expect from colony recognition compounds. Our data suggests that this is indeed the case for the alkenes, but not for the fatty acids. Fatty acid quantities varied considerably between nestmates and thus cannot function in nestmate recognition. Every colony had its own alkene profile (Figure).
The next step of our research will be to investigate whether and how Varroa mimics these recognition compounds to stay undetected in the colony. Only by better understanding the Varroa-honey bee system can we begin to disrupt this system of manipulation and design new and more effective treatments to combat this enemy common to bee and man.